Continuous crystallizing apparatus for sugar-bearing liquor

ABSTRACT

A crystallizer for sugar has a shell which is approximately cylindrical about a horizontal axis, and symmetrical relative to a vertical plane through the axis. A group of plate-shaped heating elements in the shell define a horizontal plane which upwardly bounds the group and divides the interior of the shell into a top portion and a bottom portion. The numerical value of the combined surface area in square meters of the heating elements which are upright and parallel to the axis is 13 to 20 times the numerical value of the capacity of the bottom portion in cubic meters, and the capacity of the bottom portion is 0.2 to 0.35 times the total capacity of the shell. The bottom portion is axially divided into compartments by partitions transverse to the axis.

Staees afiet 1111 3, 27,5 2

[72] Inventors Francis Dambrine FOREIGN PATENTS eh Bamuh 982 581 6/1951 France 127/53 Jean Gimghhehemmes; Jacques 1,324,801 3/1963 France 127/16 fi i'g'grgag Wham 1,444,230 5/1966 France 127/16 1,491,312 7/1967 France 127/16 [21] P 834,629 527,992 10/1940 Great Britain 127/58 [22] F11ed June 19, 1969 451 Patented Dec. 14, 1971 OTHER REFERENCES V 73 Assign, Fives Lim c fl Honig, Principles of Sugar Technology" Vol. 11, p. 307,

Paris, France 334 1959) [32] y J ly 17, 1968 Primary Examiner.loseph Scovronek [33 1 France Assistant Examiner-D. G. Conlin [31] 159451 Attorney-Kurt Kelman [54] CONTINUOUS CRYSTALUZING APPARATUS FOR ABSTRACT: A crystallizer for sugar has a shell which is ap- SUGAll-BEARINQ LIQUOR proximately cylindrical about a horizontal axis, and symmetri 1o clalmsas Drawmg Flgs. cal relative to a vertical plane through the axis. A group of 52 us. 01 127/16, Plate-Shaped heating elements in define a hrilhtal 23/273, 127/15, 127/58, 127/61 plane which upwardly bounds the group and divides the interi- 51 1 rm. (:1 C13! 1/02, or a P Portion and hohom P" The C13g H00, Cl3g 1/04 merical value of the combined surface area in square meters 501 Field 61 Search 127/15, 16, of the healing elements which are upright and Parhllel the 2947 58 6044; 23/273, 303 axis is 13 to 20 times the numerical value ofthe capacity of the bottom portion in cubic meters, and the capacity of the bot- References Cited tom portion is 0.2 to 0.35 times the total capacity of the shell. UNITED STATES PATENTS The bottomportion is axially divided into compartments by 2,091,900 8/1937 Widmer partitions transverse to the axis.

PAIEIIIEE UEcI I ILII 3,627,582

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| FRANCIS DAMBRINE JEAN c. GIORGI JACQUES DE CREMOUX BY AGENT PATENTED 0501 4 ml SHEET 2 [1F 2 E mm UAR WW LA D s C N A R F JEAN C. GIORGI JACQUES DE CREMOUX AGENT CONTINUOUS CRYSTALLIZING APPARATUS FOR SUGAR-BEARING LIQUOR BACKGROUND OF THE INVENTION This invention relates to crystallizing equipment, and particularly to a crystallizing apparatus suitable for crystallizing sugar and similar materials.

The invention is more specifically concerned with an improvement in crystallizing equipment in which an approximately cylindrical shell having a horizontal axis and an upright plane of symmetry through the axis has an interior divided into compartments by partitions which are perpendicular to the axis, and a group of heating elements in the bottom portion of the shell extends over the entire axial length of the shell.

In the normal operation of such apparatus, crystallization nuclei are formed dimensions supplied in the first compartment to which seen sugar-bearing supersaturated liquor is fed. The nuclei and the crystals growing on them are carried by the liquid axially through the successfully from compartment to compartments through openings in the partitions. A portion of the water in the liquor is evaporated in each compartment to maintain the desired composition of the massecuite which forms in the shell.

The heating elements which usually extend through several or all compartments perform a double function. They cause evaporation of the water from the liquor. They also promote circulation of the liquor in each compartment in a plane perpendicular to the shell axis to keep the massecuite substantially homogeneous and to increase the rate of crystallization.

SUMMARY OF THE INVENTION It has now been found that certain dimensional relationships in an apparatus of type described, in combination with specific structural features, are critical in obtaining optimum performance. These relationships exist between the useful capacity and the total capacity of the shell, and between the combined heating surface of the group of plate-shaped heating elements per unit of axial length and the cross section of the useful portion of the shell. The useful portion of the shell is that portion in which effective heat transfer between the heating elements and the massecuite in the shell can take place. It includes, but is not limited to, the bottom portion of the shell interior below a horizontally extending plane which upwardly bounds the group of heating elements. The capacity of the bottom portion is the internal volume of the shell below the last-mentioned plane less the space occupied by the heating elements. Each plate-shaped heating element has two wide or major, opposite, outer surfaces and a narrow, annular surface connecting the major surface. The effective heating surface of each element is the surface portion which is exposed to the massecuite, and essentially determined by the area of the major surfaces.

In the apparatus of the invention, the capacity of the bottom portion of the shell, as defined above, is 0.2 to 0.35 times the total capacity of the shell, and the numerical ratio of the combined heating surfaces of the elements in square meters per meter of axial length of the group to the cross section of the shell bottom portion in square meters is between 13:1 and :1.

Other features, additional objects and many of the attendant advantages of this invention will readily be appreciated as the invention becomes better understood by reference to the following detailed description if considered in connection with the appended drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 shows a crystallization apparatus of the invention in side-elevational section through the axis of the crystallizer shell;

FIG. 2 illustrates the shell of FIG. 1 in front elevational section; and

FIGS. 3 and 4 show modified shells in views corresponding to that ofFIG. 2; and

FIG. 5 shows a modification of the apparatus of FIGS. 1 and 2 in front elevational section.

DESCRIPTION OF THE PREFERRED EMBODIMENT 0 crystallizer 12, with which this invention is more specifically concerned, has a horizontally elongated shell 13 whose shape is that of a cylinder, the term being used broadly and not limited to a circular cylinder. As is seen in FIG. 2, the shell 13 has two wall portions of semicircular cross section connected by narrow, flat, vertical wall portions.

In a typical installation of the invention, the length of the shell 13 is 8 to 15 meters, and its horizontal width between 2 and 4.5 meters. If the cross-sectional shape shown in FIG. 2 is selected, the flat wall portions have a height of 0.6 to 1 meter.

The interior of the shell 13 is partly divided into compartments by partitions 14 perpendicular to the upright, longitudinal plane of symmetry of the shell which rise from the shell bottom and have openings near the bottom which connect axially juxtaposed compartments. The illustrated apparatus has seven compartments, but the number of compartments may be increased to about l2,and may be reduced to three or four if the sugar-bearing liquor in the shell 13 is seeded with sugar crystals formed in another stage of the apparatus.

The several compartments vary in length and become larger in the direction of material flow through the shell 13, that is, from the left to the right, as viewed in FIG. 1, so that the dwell time of the material is the same within $30 percent in each compartment. The length of the first compartment entered by the liquor should be at least 0.5 meter to permit access by a maintenance man.

The steam developed in the crystallizer is withdrawn through nipples 16 in the top portion of the shell 13 by suction equipment, conventional in itself and not shown.

The thermal energy for operation of the crystallizer is mainly supplied by steam in two longitudinally aligned groups of heating elements 20 which are hollow plates arranged in the bottom portion of the shell 13. The major surfaces of the elements 20 are parallel to each other and upright, and are also parallel to the vertical, longitudinal plane of symmetry of the shell.

Each group 18 of heating elements extends through several compartments, the partitions 14 being slotted to permit passage of the individual heating plates 20. The plates 20 are of practically uniform cross section over the entire length of each group 18, and the longitudinally aligned elements 20 of the two groups 18 have the same cross section. Each group as a whole approximately conforms to the inner wall of the shell bottom, as is best seen in FIG. 2, becoming wider in an upward direction and being of uniform cross section over its entire axial length.

The plates 20 of each group 18 pass through an end wall of the shell 13 into a steam chest 26 connected to a steam supply system 27 indicated in broken lines, and the plates 20 are also connected with a condensate collecting system 28.

The dimensions of the groups 18 of heating elements 20 are chosen in such a manner that the numerical ratio between the capacity of the shell bottom below an approximately horizontal plane 30 defined by the top ends of the plates 20 and the total capacity of the shell is between 0.2 and 0.35. The numerical value of the total effective heating surface of the two groups 18 of heating elements 20, when expressed in square meters, is 13 to 20 times the numerical value of the shell capacity below the plane 30 expressed in cubic meters. The last-defined relationship is equal to the numerical ratio of the heating surface per meter of axial length to the cross section of the shell bottom portion upwardly bounded by the plane 30, expressed in consistent units of area.

The useful volume of the apparatus, that is, the volume occupied by massecuite in normal operation is approximately 1.4 times the capacity of the shell bottom below the plane 30, or 0.3 to 0.5 times the total shell capacity. The ratio between the numerical value of the total heating surface area, in square meters, to the numerical value of the useful volume of the apparatus, in square meters, is therefore 9 to 14.

As is indicated in the partly diagrammatic representation of FIG. 1, unsaturated sugar-bearing liquor is supplied through a pipe system 40 and partly fed to the evaporator 10 where it is concentrated, and partly to the individual compartments of the crystallizer 12. A minor fraction of the unsaturated liquid is introduced into the mixer 34 where it is mixed with seed crystals. The slurry or magma formed in the mixer contains 30 to 60 percent crystals and is fed to the first compartment of the crystallizer 12, together with concentrated liquor discharged from the evaporator 10.

The supply of unsaturated juice to the first two compartments is automatically controlled in a conventional manner, not shown, to maintain selected fixed sugar concentrations in these compartments. The supply of unsaturated juice to the other compartments is controlled in such a manner as to maintain a desired percentage ratio of crystals or of solids in the massecuite discharged from the manner, not shown, to maintain selected fixed sugar concentrations in these compartments. The supply of unsaturated juice to the other compartments is controlled in such a manner as to maintain a desired percentage ratio of crystals or of solids in the massecuite discharged from the crystallizer. Nonillustrated sensing devices responsive to the specific gravity of the material in the shell 13 or of the discharged material operate valves 42 in the pipe system 40.

The crystals in the massecuite grow during their passage through the several compartments, and the massecuite is ultimately withdrawn from the shell 13 by a pump 36 whose output is controlled in a conventional, nonillustrated manner to maintain a constant massecuite level in the shell K3.

in order to prevent deposition of crystals on the interior wall surfaces of the shell 13 and on the heating plates 20, the exposed surfaces are made of polished stainless steel. The bottom portion of the shell 13 is enveloped by a heating jacket 32 (FIG. 2) which is supplied with a heated fluid. The top portions of the walls in each compartment which are not immersed in the massecuite are coated with the unsaturated juice which is supplied to each compartment.

A film of unsaturated liquid may be maintained on the exposed wall portions above the massecuite level with discharge from perforated pipes 33 arranged near the top of each compartment. Since the amount of unsaturated jiuce supplied to each compartment is generally insuflicient to flood all upright walls of the compartment at the same time, several pipe sections may be arranged about the circumference of the compartment and supplied sequentially with juice thorough a rotary nonillustrated distribution valve, each section being fed at a rate sufficient to cause thorough wetting of the associated wall portion.

The movement of the massecuite transversely to the axis of the shell i3 is enhanced by steam injected into the bottom of each compartment below the heating plates 26) by pipes 38 fastened to the top of the shell and coated with unsaturated sugar juice as far as they are not immersed in the massecuite. The immersed portion of each steam pipe 38 may be protected either by a nonillustrated heating jacket or by a coating of polytetrafluoroethylene which prevents adhesion of sugar crystals. A small amount of unsaturated sugar solution may be introduced with the steam through the pipes 38 in order to prevent crystallization at the pipe orifices.

In the illustrated embodiment of the invention, the steam injected into the individual compartments of the crystallizer i2 is drawn from the calandria of the evaporator 10.

The output of a crystallizer of the type illustrated may be increased by extending its axial length, or by arranging two or more devices of the type shown in series. Other modifications and variations of the embodiment of the invention described above will readily suggest themselves to those skilled in the art.

Thus, the cross-sectional shape of the shell 13 shown in FIG. 2 may be modified without sacrificing the advantages achieved. As seen in H6. 3, the crystallizer may be provided with a shell 13' having a circular cross section, or the shell may assume the cross-sectional shape indicated at 13" in FIG. d, in which the top portion of the shell is semicircular in cross section whereas the bottom portion is a trough having a rounded V-shaped in cross section.

FIG. 5 shows a modified device for preventing deposition of sugar crystals on exposed metal surfaces in the shell 33, the view corresponding to that of FIG. 2. The section is taken through one of the compartments in the shell 12 and shows one of the partitions 14. A vertical pipe 43 is journaled in the top of the shell 13 in the upright, longitudinal plane of symmetry of the shell. It extends downwardly just below the upper edge of the partition 14 and carries a short horizontal nozzle 44 well above the level of massecuite in the compartment.

An electric motor 45 mounted on the shell 13 in a nonillustrated manner rotates the pipe 43 about its axis by means of a worm (not shown) and a worm wheel 46 on the pipe. The top end of the pipe $3 is connected with a feed line 47 for unsaturated sugar-bearing liquid by a rotary seal As the pipe 43 is turned by the motor 45, a jet of liquid 50 discharged from the nozzle 44 sweeps the upright metal walls of the compartment. lt will be understood that a sprinkler arrangement similar to or identical with that shown in FIG. 5 may be arranged in each compartment of the shell 13 to replace or to supplement the perforated pipes 33.

The worm and wormwheel 46 may be replaced by hingedly connected crank arms on the shaft of the motor 45 and on the pipe 43 to oscillate the nozzle 44 about the vertical axis of the pipe 43 when the motor 45 is energized.

Other modifications and variations of the apparatus illustrated and described above for the purpose of the disclosure will readily suggest themselves to those skilled in the art without departing from the spirit of the invention. Longitudinal dimensions of the individual compartments differing from those seen in FIG. 1 and more specifically described above are sometimes desirable, and the basic principles of the invention have been applied successfully to crystallizers having compartments of practically uniform length.

We claim:

1. A continuous crystallizing apparatus for sugar and the like comprising, in combination:

a. a substantially closed, horizontally elongated vessel having substantially the shape of a cylinder, the vessel being substantially symmetrical relative to an upright, longitudinal, first plane and having a top portion and a bottom portion;

b. a plurality of longitudinally spaced partitions transverse to said first plane and upright, said partitions dividing the interior of said vessel into a plurality of compartments, each partition being formed with an aperture connecting longitudinally adjacent compartments;

c. coating means for coating the inner wall of said top portion of the vessel with a liquid,

1. the coating means including a nozzle member in one of said compartments in the top portion of said vessel, moving means for angularly moving said nozzle member about a vertically extending axis, and feeding means for feeding said liquid to said nozzle member, the nozzle member having an orifice directed toward a partition and an inner wall of said vessel during said angular movement of the nozzle member; and

d. a group of heating elements in said bottom portion of said vessel and spaced from the top portion thereof;

1. each heating element including a hollow plate member having two outer, opposite, major surfaces, and an outer, minor, annular surface connecting said major surfaces,

2. said major surfaces of said plate members being upright and parallel,

3. said group being symmetrical relative to said first plane and defining a second substantially horizontal plane,

said second plane upwardly bounding said group and said bottom portion of the vessel,

4. the numerical value of the combined area of said surfaces, in square meters, being 13 to times the numerical value of the capacity of said bottom portion, in cubic meters, and the capacity of said bottom portion being 0.2 to 0.35 times the total capacity of said vessel.

2. A continuous crystallizing apparatus for sugar and the like comprising, in combination:

a. a substantially closed, horizontally elongated vessel having substantially the shape of a cylinder, the vessel being substantially symmetrical relative to an upright, longitudinal, first plane and having a top portion and a bottom portion, said vessel having a bottom wall defining the lower limit of said bottom portion;

b. a plurality of longitudinally spaced partitions transverse to said first plane and upright, said partitions dividing the interior of said vessel into a plurality of compartments, each partition being formed with an aperture connecting longitudinally adjacent compartments;

c. a group of heating elements in said bottom portion of said vessel spaced upwardly from said bottom wall and spaced from the top portion of said vessel;

1. each heating element including a hollow plate member having two outer, opposite, major surfaces, and an outer, minor, annular surface connecting said major surfaces,

2. said major surfaces of said plate members being upright and parallel,

3. said group being symmetrical relative to said first plane and defining a second substantially horizontal plane, said second plane upwardly bounding said group and said bottom portion of the vessel,

4. the numerical value of the combined area of said surfaces, in square meters, being 13 to 20 times the numerical value of the capacity of said bottom portion, in cubic meters, and the capacity of said bottom portion being 0.2 to 0.35 times the total capacity of said vessel,

d. coating means for coating the inner wall of said top portion with a liquid; and

e. injecting means for injecting steam into said bottom portion, said injecting means including a conduit having an orifice between said group of heating elements and said bottom wall.

3. An apparatus as set forth in claim 2, further comprising evaporator means for partly evaporating a dilute juice so as to produce a more concentrated liquor and steam, a pipe connecting said evaporator means to said injecting means for transferring said steam to said injecting means, nd feeding means for feeding said more concentrated liquor to said shell.

4. A continuous crystallizing apparatus for sugar and the like comprising, in combination:

a. a substantially closed, horizontally elongated vessel having substantially the shape of a cylinder, said vessel having a top portion, a bottom portion and a bottom wall defining the lower limit of said bottom portion;

b. a plurality of longitudinally spaced partitions transverse to the longitudinal axis of said vessel, said partitions dividing the interior of said vessel into a plurality of compartments, each partition being formed with an aperture connecting longitudinally adjacent compartments;

c. a group of heating elements in said bottom portion of said vessel spaced upwardly from said bottom wall; and

d. means for injecting steam into said bottom portion below said group of heating elements therein.

5. An apparatus as set forth in claim 4, wherein said injecting means includes at least one conduit having an orifice positioned between said group of heating elements and said bottom wall.

6. An apparatus as set forth in claim 4, including a heating jacket enveloping at least part of said bottom portion.

'7. An apparatus as set forth in claim 4, including means for coating the inner wall of said top portion with a liquid.

8. An apparatus as set forth in clarm 41, rncludrng evaporator means for partially evaporating a dilute juice so as to produce a concentrated liquor and steam, a pipe connecting said evaporator means to said injecting means for transferring said steam to said injecting means, and feed means for feeding said concentrated liquor to said shell.

9. An apparatus as set forth in claim 8, including mixer means for mixing seed crystals with a carrier liquid,'and a conduit connecting said mixer means to said vessel for transfer of the mixture of seed crystals and carrier from said mixer means to said vessel.

10. In a continuous crystallizing apparatus for sugar and the like wherein a substantially closed cylindrically shaped vessel having a top portion, bottom portion and a bottom wall defining the lower limit of the bottom portion has a group of heating elements in said bottom portion spaced upwardly from said bottom wall, the improvement comprising means for injecting steam into said bottom portion below said group of heating elements therein. 

2. A continuous crystallizing apparatus for sugar and the like comprising, in combination: a. a substantially closed, horizontally elongated vessel having substantially the shape of a cylinder, the vessel being substantially symmetrical relative to an upright, longitudinal, first plane and having a top portion and a bottom portion, said vessel having a bottom wall defining the lower limit of said bottom portion; b. a plurality of longitudinally spaced partitions transverse to said first plane and upright, said partitions dividing the interior of said vessel into a plurality of compartments, each partition being formed with an aperture connecting longitudinally adjacent compartments; c. a group of heating elements in said bottom portion of said vessel spaced upwardly from said bottom wall and spaced from the top portion of said vessel;
 2. said major surfaces of said plate members being upright and parallel,
 2. said major surfaces of said plate members being upright and parallel,
 3. said group being symmetrical relative to said first plane and defining a second substantially horizontal plane, said second plane upwardly bounding said group and said bottom portion of the vessel,
 3. said group being symmetrical relative to said first plane and defining a second substantially horizontal plane, said second plane upwardly bounding said group and said bottom portion of the vessel,
 3. An apparatus as set forth in claim 2, further comprising evaporator means for partly evaporating a dilute juice so as to produce a more concentrated liquor and steam, a pipe connecting said evaporator means to said injecting means for transferring said steam to said injecting means, nd feeding means for feeding said more concentrated liquor to said shell.
 4. A continuous crystallizing apparatus for sugar and the like comprising, in combination: a. a substantially closed, horizontally elongated vessel having substantially the shape of a cylinder, said vessel having a top portion, a bottom portion and a bottom wall defining the lower limit of said bottom portion; b. a plurality of longitudinally spaced partitions transverse to the longitudinal axis of said vessel, said partitions dividing the interior of said vessel into a plurality of compartments, each partition being formed with an aperture connecting longitudinally adjacent compartments; c. a group of heating elements in said bottom portion of said vessel spaced upwardly from said bottom wall; and d. means for injecting steam into said bottom portion below said group of heating elements therein.
 4. the numerical value of the combined area of said surfaces, in square meters, being 13 to 20 times the numerical value of the capacity of said bottom portion, in cubic meters, and the capacity of said bottom portion being 0.2 to 0.35 times the total capacity of said vessel, d. coating means for coating the inner wall of said top portion with a liquid; and e. injecting means for injecting steam into said bottom portion, said injecting means including a condUit having an orifice between said group of heating elements and said bottom wall.
 4. the numerical value of the combined area of said surfaces, in square meters, being 13 to 20 times the numerical value of the capacity of said bottom portion, in cubic meters, and the capacity of said bottom portion being 0.2 to 0.35 times the total capacity of said vessel.
 5. An apparatus as set forth in claim 4, wherein said injecting means includes at least one conduit having an orifice positioned between said group of heating elements and said bottom wall.
 6. An apparatus as set forth in claim 4, including a heating jacket enveloping at least part of said bottom portion.
 7. An apparatus as set forth in claim 4, including means for coating the inner wall of said top portion with a liquid.
 8. An apparatus as set forth in claim 4, including evaporator means for partially evaporating a dilute juice so as to produce a concentrated liquor and steam, a pipe connecting said evaporator means to said injecting means for transferring said steam to said injecting means, and feed means for feeding said concentrated liquor to said shell.
 9. An apparatus as set forth in claim 8, including mixer means for mixing seed crystals with a carrier liquid, and a conduit connecting said mixer means to said vessel for transfer of the mixture of seed crystals and carrier from said mixer means to said vessel.
 10. In a continuous crystallizing apparatus for sugar and the like wherein a substantially closed cylindrically shaped vessel having a top portion, bottom portion and a bottom wall defining the lower limit of the bottom portion has a group of heating elements in said bottom portion spaced upwardly from said bottom wall, the improvement comprising means for injecting steam into said bottom portion below said group of heating elements therein. 